This invention relates to an electronically controlled timepiece, and more particularly to an electronic watch utilizing a time indicating body comprising a multitude of liquid crystal display elements.
Recently, several types of clocks and watches utilizing liquid crystal display elements for the time indication have been developed and are attracting attention of consumers. However, most of these types of time display devices are so-called "digital time display" in which the time is represented in the form of numerals. And there has not been existed or put into practical use such an electronically controlled timepiece especially an electronic wrist watch wherein a time display body comprises a multitude of time indicating sections visualized by the electro-optical effect of liquid crystals, and the time is expressed analogically in the form of the various display patterns with time information which appear on the display face of the time indicating body.
On the other hand, there have been many studies on properties of various types of liquid crystal materials lately. Among them, nematic liquid crystals, in particular, are found to work as an effective medium in the application to display devices. It is also well known that there are two types in nematic liquid crystals, that is, the dynamic light scattering mode and the field effect mode. In the liquid crystal with the dynamic scattering mode, turbulence in the molecule alignment is caused when a pertinent electric field is applied across the layer of the liquid crystal confined between a pair of electrode plates. As a result, incident lights are diffused due to this turbulence created within the specific portion of the liquid crystal across which a voltage above the threshold level is applied causing the liquid crystal within this portion to change from clear to "frosted" appearance.
The liquid crystals with the field effect mode can be further classified into two types. One of them has positive dielectric anisotropy within its molecules, and the other has negative dielelctric anistropy. When these field effect mode liquid crystals are applied to a liquid crystal display cell which is composed of a pair of Nesa glasses having a plurality of electrodes coated on its opposing surfaces and the liquid crystal confined therebetween, in the case of the liquid crystal with positive dielectric anisotropy, the longitudinal axes of the molecules are so oriented to align in parallel with the plane of the electrodes provided on said pair of glasses, whereas in the case of the liquid crystal with negative dielectric anisotropy, the longitudinal axes of the molecules are perpendicularly aligned to the plane of said electrodes. It is perceivable with the aid of a pair of polarizers that, within these two types of the field effect mode liquid crystals, changes in their molecules alignment are caused in response to application of an electric field. Taking advantage of these characteristics, the nematic liquid crystals of these kinds are widely utilized for various display devices to indicate letters, numerals or figures.
Further, liquid crystals of these types have another advantage of being operable at relatively lower power consumption due to high resistivity close to that of insulators, and the threshold voltage is extremely lower than other electro-luminous substances. Therefore, they have many potentials for application in wide range of measurement devices including portable electronic calculators and horological devices etc. However, there still are a number of problems to be solved in practical application of such a liquid crystal time display device in which a pair of electrode plates constituting an indicating board are equipped with a multitude of sectioned electrodes which constitute unit display elements and the time is indicated by the complicated display patterns created on the display surface with this multitude of display elements.
Still further, in order to drive such a multitude of display elements by conventional driving method, it is necessary to draw out leads from each of these unit electrodes individually and to connect them with corresponding output terminals of the electronic circuits with output systems through respective switching means. As a result, number of such connection leads and switching means will be greatly increased and the distribution works will become very much complicated. Especially, in application of said display elements to such a small size display device as a wrist watch, this defect presents serious problem. Namely, a wide space needed for the distribution of such a large number of leads and a large volume required for the connectors and other components will make it impracticable to house them within the limited space. Further, it tends to cause such troubles as miswiring of the leads or short circuits. In case the part of an electronic circuit having a time output mechanism is constructed with LSI (Large Scale Intergrated Circuit) comprising logic circuit to actuate a multitude of display elements at predetermined cycle, it will involve much difficulty even with the present state of the art technique because the required leads to be brought out from the LSI increase greatly in number, and the package to house the LSI must be expanded only because it is technically difficult to bring out such multitude of leads from the minute LSI. Accordingly, advantage to be anticipated from the employment of the LSI is well offset by such unreasonably large space needed only to accommodate these connection means. Consequently, it has been impracticable with conventional methods to apply the liquid crystal display device as described above to such a compact display device as a wrist watch. Moreover, in order to perform accumulative display by turning ON these multitude of display sections in sequence, there are still more problem to be solved, for example, life of the liquid crystal or contrast between ON sections and OFF sections and other technical problems.